Ruby
Mohs hardness 9, Specific gravity 4, Refractive index 1.760–1.770. A ruby is a pink to blood-red gemstone, a variety of the mineral corundum (aluminium oxide). The red colour is caused mainly by the presence of the element chromium. Its name comes from ruber, Latin for red. Other varieties of gem-quality corundum are called sapphires. The ruby is considered one of the four precious stones, together with the sapphire, the emerald, and the diamond. Rubies have historically been mined in Thailand, Cambodia, and in Afghanistan. Rubies have been found in Sri Lanka. After the Second World War ruby deposits were found in Tanzania, Madagascar, Vietnam, Nepal, Tajikistan, and Pakistan. A few rubies have been found in the U.S. states of Montana, North Carolina, and South Carolina. More recently, large ruby deposits have been found under the receding ice shelf of Greenland. In 2002 rubies were found in the Waseges River area of Kenya.
Prices of rubies are primarily determined by colour. The brightest and most valuable "red" called pigeon blood-red, commands a huge premium over other rubies of similar quality. After colour follows clarity: similar to diamonds, a clear stone will command a premium, but a ruby without any needle-like rutile inclusions may indicate that the stone has been treated. Cut and carat (weight) also determine the price. All natural rubies have imperfections in them, including colour impurities and inclusions of rutile needles known as "silk". Gemmologists use these needle inclusions found in natural rubies to distinguish them from synthetics, simulants, or substitutes. Usually the rough stone is heated before cutting. Almost all rubies today are treated in some form, with heat treatment being the most common practice. However, rubies that are completely untreated but still of excellent quality command a large premium.

RUBY - fosters integrity, devotion, happiness, healing, courage, passion, romance, enthusiasm and generosity. Also evokes warmth, generosity, inspiration, prosperity, high energy, power and leadership ability.

Zodiac gemstone for Capricorn: ruby
Guardian angel Malchediel his talisman stone ruby
July modern birthstone - ruby, ancient traditional birthstones: Polish - ruby and Russian -  ruby
August ancient traditional birthstone  Hindu - ruby
December ancient traditional birthstones: Hebrew - ruby, Roman - ruby, Arabic - ruby

The Twelve Apostles  Christianity influenced the symbolism of gemstones. Specific gemstones were also associated with the twelve apostles. Apostle Andrew associated with the Ruby.

Ruby care: Wash with warm soapy water, Avoid harsh detergents, Ultrasonic and steam cleaning are usually safe.